Patent Application
20090221422
This invention relates to a hand-held device for emitting a laser beam. In particular, this invention relates to a compact, high power laser device having an internal power supply.
Lasers have been widely used for marking of substrates, typically by ablation but also by causing material, that can absorb laser energy, to char or to change colour. WO97/47397 discloses a method and apparatus for marking a product with identification indicia. A coating layer is formed on the substrate to be marked. The coating layer contains an additive that is darkenable under the action of a CO2 laser beam. CO2 lasers have typically been used for this purpose due to their long operating lives of at least 10,000 operating hours. The coating is darkenable upon irradiation with focused energy of the laser source.
Lasers have also been widely used to achieve welding by use of curable formulations, typically in the near infrared region using, for example, carbon black. Other curing applications are also known, for example in the curing of adhesives or sealants.
Whilst many large scale marking/printing and curing applications are known using laser energy sources, these generally involve large, expensive apparatus having a long setup time and high power consumption.
In accordance with a first aspect, the present invention is a hand-held device for emitting a laser beam, the device comprising a laser source having a power rating of at least 10 mW, an internal power supply adapted to supply power to the power source, and at least one optical element for manipulating, in use, a beam produced by the laser source.
The device of the present invention is advantageous in that it is small, easily manipulable and self contained, yet emits a laser beam of sufficient energy for use in small to very small scale printing and/or curing applications of the order of centimetres or less.
In accordance with a second aspect, the present invention is a method of ink-less printing comprising providing a substrate including an additive susceptible to changing colour when energized by a laser, providing a hand-held device in accordance with the first aspect of the present invention, positioning the hand-held device over the substrate, and energizing the laser source to cause the device to emit a laser beam such that at least one desired point on the substrate is energized by the beam thus causing the additive to change colour at said point.
In accordance with a third aspect, the present invention is a method of curing a substrate comprising providing a substrate to be cured when energized by a laser, providing a hand-held device in accordance with the first aspect of the present invention, positioning the hand-held device over the substrate, and energizing the laser source to cause the device to emit a laser beam such that the substrate is energized by the beam thus causing curing of the substrate.
The hand-held device in accordance with the first aspect of the present invention may have an infrared, visible or UV laser source. The device has at least one optical element which may be a focusing lens, preferably an auto focus lens, and/or a collimating lens. The optical element may further be a mask through which at least some of the laser beam passes before leaving the device. The mask may be provided in addition to other optical elements. A latent image formed on the mask may be fixed or may be variable, for example a liquid crystal optical shutter array, which may be pre-programmed or actively controlled. The internal power supply is preferably a battery which may be removable and may be rechargeable.
The laser source may be a laser diode, a fibre-coupled laser diode, a laser array, or a diode-pumped solid-state laser. The power rating of the laser source may be between 10 to 20 mW, 20 to 30 mW, 30 to 40 mW, 40 to 50 mW, 50 to 100 mW, 100 to 200 mW, 200 to 500 mW, 500 mW to 1 W, 1 to 10 W, 10 to 20 W, 20 to 50 W, 50 to 100 W, or any combination of these ranges. The power rating of the laser source may be selected depending on the application and its power output may be fixed, or may be actively or passively controlled within that rating. The hand-held device preferably has a button which, when depressed by a user, energizes the laser source. Once energized, the laser source remains energized either until the button, or other user input means, is released, or otherwise disengaged, or the device may be adapted such that the laser source remains energized for a predetermined period before being automatically de-energized.
In a preferred embodiment, the device further comprises a photo-receiver which is preferably a photo-diode which may have an optical filter disposed upstream of the photo-receiver in a direction of received light. The optical filter is preferably a narrow bandwidth filter.
The device may be in the form of a pen, particularly for use in laser “writing” applications, or may have any other suitable ergonomic shape depending on the application.
The embodiments of the present invention will now be described with reference to the accompanying drawings in which:
Turning first to
The hand-held device described above is suitable for use in ink-less printing, marking and curing applications. In each of these applications the device is to be positioned such that the shielding element 9 is adjacent a substrate 10 to be printed, marked or cured. The device should be positioned such that the optical axis of the laser beam 8 is substantially perpendicular to a surface of the substrate 10 to be irradiated. The control electronics module 4 may be adapted such that upon depression of the button 5, the laser diode 2 is supplied with power from the battery 3 for a predetermined period of time. Alternatively, the control electronics module 4 may be adapted to continue to supply power from the battery 3 to the laser diode 2 until the user once again depresses the button 5. In either case, the irradiating period should be adapted such that a fluence level required by the substrate 10 to effect the appropriate marking or curing application is obtained.
The power output of the laser diode 2 may be fixed, for example at the maximum power rating of the laser diode 2, or may be fixed at a power level below that of the maximum power rating of the laser diode 2. Alternatively, the power output of the laser diode 2 may be variable and controlled by the control electronics module 4. The optical element 7 may be a collimating, focusing or auto-focusing lens or a combination of these. Element 7 may further include a mask having a latent image formed thereon. The latent image of the mask may be either fixed or variable and controlled by the control electronics module 4. The mask selectively allows passage of at least some of the laser beam 6 to pass therethrough to form laser beam 8. A suitable mask may be an LCD optical shutter array or the like. Details of such an optical shutter array are provided in applicants co-pending British Patent Application No. 0520115.7.
The hand-held device of
By altering the focal length of the optical element 7, the size of the spot or image footprint on the surface of the substrate 10 may be increased such that the printed image increases in size. However, this will require either a higher laser diode 2 power output or an increase in exposure time for like substrates 10. In any such security printing the matching of the hand-held laser device to the substrate improves the security of the document to be printed since it can only be reproduced where a forger has access to both the substrate and the hand-held device.
The printing of micro-dots or micro-signatures has further application in the field of supply chain verification and/or inspection of branded goods. It is often desirable that any such verification is marked on the goods themselves. However, in certain applications it is desirable that this marking is not readily visible to an end user. This may be achieved by either marking the substrate such that the mark is only visible under ultraviolet or infrared light, or is so small as to be invisible to the naked eye. Marking of passports and other identification documents is also foreseen using this technique.
Another potential application of the present invention is in the field of tattoos. It is conceived that a suitable transparent coating may be applied to the skin which is subsequently irradiated using the hand-held device in accordance with the present invention to effect a colour change in order to image the tattoo. Depending on the coating formulation, a monochrome, grayscale or full multi-tonal colour image may be developed from a single exposure using the device. It is also conceived that, so long as laser safety regulations may be complied with, the hand-held device may be used to image substrates directly without the application of a suitable coating formulation.
In the field of curing applications for small scale curing it is advantageous that the formulation being cured exhibits a colour change following exposure at a predetermined fluence level. For example, the same formulation undergoing curing may change colour after a predetermined interval at a particular exposure intensity level corresponding to the same level required to effect the curing. Suitable curing substrates are many polymers and ceramics and pre-ceramics having diverse applications from cosmetic treatments to hand crafting. By altering the concentration of additives susceptible to changing colour in particular locations it becomes possible to effect a different colour change under the same fluence level to that of an adjacent point on the substrate. This is particularly useful where it is required to image a micro-signature or date stamp for the particular curing procedure. Verification of such marking may be effected using the embodiment of
For large de-magnifications, several relay image systems can be cascaded in series, simply using the image plane of one system to act as the virtual mask for the next system. This negates the requirement for large path lengths (de-magnification v/u). Conversely, if a single de-magnification is preferred and consequently large path links are required, the path can be conceded/folded using mirrors allowing in the compact design to be utilized.
In the system of
An alternative mode of operation could utilize the Fourier transform imaging in a focus geometry. To accomplish this the mask 7c must be replaced by a Fourier image mask of the required final image at the focus of the lens 7d instead of the image plane on the substrate 10 as per relay imaging. A simple focusing lens would then generate very detailed images in a small spot. Moreover, this also facilitates use of a relatively simple compact arrangement comprised of a single lens and Fourier image mask.
It is also envisaged that the optical element 7 could be replaced or include a holographic element or optical setup capable of generating a holographic image on the substrate 10.
It is envisaged that the battery 3 of the hand-held device may be either a rechargeable battery having a suitable connection to a charger, or a removable battery to be replaced where necessary. Although the device has been described with reference to a laser diode as the laser source, it is specifically intended that a fibre-coupled laser diode, a laser array, or a diode-pumped solid-state laser may be used instead. The power rating of the laser source, so as to be suitable for the particular applications described above, is at least 10 mW. However, it will be appreciated that a power rating of between 10 to 20 mW, 20 to 30 mW, 30 to 40 mW, 40 to 50 mW, 50 to 100 mW, 100 to 200 mW, 200 to 500 mW, 500 mW to 1 W, 1 to 10 W, 10 to 20 W, 20 to 50 W, 50 to 100 W, or any combination of these ranges may be suitable depending on the particular application.
In addition to the substrate materials described above, the following substrate materials may be suitable for use in the methods of the present invention as defined by the appending claims: metals, alloys, glasses, ceramics, plastics, fabrics, wood, paper, card, resins, rubbers, foams, composites, stone, walls and body tissue. Substrate materials for use in curing applications may, in particular, be adhesives, sealants or dental composites.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0522974.5 | Nov 2005 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB06/04177 | 11/8/2006 | WO | 00 | 9/22/2008 |
